Maria Elisa Scarpelli Ribeiro e Silva

Preparation and thermal study of polymers derived from acrylamide

Abstract Polyacrylamide (PAA) and some of its N -alkyl substituted derivatives have been synthesised and characterised using thermal analysis. Thermal stability was studied by thermogravimetry (TG) and differential scanning calorimetry (DSC) was used to determine the glass transition temperatures ( T g ). The results showed an increase in degradation temperature ( T d ) as the hydrogens of the amide nitrogen were replaced by alkyl groups. An opposite tendency was verified for T g values. The observed increase in T d values is discussed in terms of the formation of an intermediate ion in the degradation, while the decrease in T g values is discussed in terms of polymer–polymer interactions such as hydrogen bonds.

Bioartificial polymeric materials based on collagen and poly(N-isopropylacrylamide)

Films of collagen (CLG) and poly(N-isopropylacrylamide), PNIPAAm, were prepared by casting from water solutions. These bioartificial polymeric materials were studied to examine the influence of PNIPAAm content and glutaraldehyde vapor cross-linking on the thermal and biological stability of CLG. Mixtures, ranging from 20-80 wt% CLG composition, were cross-linked through exposure to glutaraldehyde vapors. Thermal and morphological properties of the films, cross-linked or not, were investigated by differential scanning calorimetry, thermogravimetry, and scanning electron microscopy, with the aim of evaluating miscibility, thermal stability, and interactions among the constituents. The experimental results indicated that the homopolymers are not thermodynamically compatible. However, there is good evidence that effective interactions, probably due to hydrogen bond formation, takes place between the constituents. These interactions are more evident on the samples that were not cross-linked. DSC studies revealed that PNIPAAm exerts a thermal stabilizing effect on uncross-linked CLG, while the cross-linking with glutaraldehyde affects only the biological polymer, preventing the interactions with PNIPAAm. SEM micrographs of the uncross-linked mixtures showed that the morphology, in all compositions studied, remains similar to the pure collagen. In the corresponding cross-linked samples, a more compact aggregation is observed although no appreciably changes can be seen.

Síntese e caracterização do copolímero poli(3-hidroxibutirato-co-E-caprolactona) a partir de poli (3-hidroxibutirato) e poli(E-caprolactona)

In the present work, the copolymer poly(3-hydroxybutyrate-co-e-caprolactone), P(HB-co-CL), was prepared by transesterification reaction from PHB and PCL. Zirconium (IV) acetylacetonate was used as catalyst and the copolymers were obtained in a wide range of compositions of PHB/PCL (20/80, 50/50, 80/20). These copolymers were characterized by GPC, FT-IR, 1H-NMR, 13C-NMR, TG, and DSC. The copolymers had weight average molecular weight less than 24.000 Daltons. All the systems were thermally more stable than PHB, showing lower crystallinity than the homopolymers. These materials are good candidates to be used as biomaterials, in drug release matrices, or even as PHB/PCL blends compatibilizers.

Molecularly imprinted polymer for determination of lumefantrine in human plasma through chemometric-assisted solid-phase extraction and liquid chromatography

Lumefantrine is the first-choice treatment of Falciparum uncomplicated malaria. Recent findings of resistance to lumefantrine has brought attention for the importance of therapeutic monitoring, since exposure to subtherapeutic doses of antimalarials after administration is a major cause of selection of resistant parasites. Therefore, this study focused on the development of innovative, selective, less expensive and stable molecularly imprinted polymers (MIPs) for solid-phase extraction (SPE) of lumefantrine from human plasma to be used in drug monitoring. Polymers were synthesized by precipitation polymerization and chemometric tools (Box-Behnken design and surface response methodology) were employed for rational optimization of synthetic parameters. Optimum conditions were achieved with 2-vinylpyridine as monomer, ethylene glycol dimethacrylate as crosslinker and toluene as porogen, at molar ratio of 1:6:30 of template/monomer/crosslinker and azo-bisisobutyronitrile as initiator at 65 °C. The MIP obtained was characterized and exhibited high thermal stability, adequate surface morphology and porosity characteristics and high binding properties, with high affinity (adsorption capacity of 977.83 μg g-1) and selectivity (imprinting factor of 2.44; and selectivity factor of 1.48 and selectivity constant of 1.44 compared with halofantrine). Doehlert matrix and fractional designs were satisfactorily used for development and optimization of a MISPE-HPLC-UV method for determination of lumefantrine. The method fulfilled all validation parameters, with recoveries ranging from 83.68% to 85.42%, and was applied for quantitation of the drug in plasma from two healthy volunteers, with results of 1407.89 and 1271.35 ng mL-1, respectively. Therefore, the MISPE-HPLC-UV method optimized through chemometrics provided a rapid, highly selective, less expensive and reproducible approach for lumefantrine drug monitoring.

Síntese e caracterização de MIP com fenilalanina visando sua aplicação na técnica de SPE

Polimeros Molecularmente Impressos (MIPs) sao polimeros sinteticos que apresentam alta seletividade a uma molecula de interesse. O objetivo deste trabalho foi a sintese e caracterizacao de MIPs para aplicacao na extracao em fase solida (SPE), visando a determinacao de fenilalanina. Os MIPs foram sintetizados a partir do MAA, fenilalanina, EGDMA, AIBN, em cloroformio. Tambem foi sintetizado o polimero nao-impresso (NIP), para controle da seletividade dos MIPs. A dessorcao da fenilalanina foi realizada em extrator Soxhlet. Os MIPs e NIP foram caracterizados pelas tecnicas de analise: FTIR, UV-Vis, MEV, DSC e TG. O MIP apresentou maior capacidade adsortiva a fenilalanina do que o NIP, com uma taxa media de adsorcao de 55% comparada a 11% para o NIP. Por MEV o MIP apresentou superficie mais porosa, importante caracteristica para aplicacao em SPE. Os estudos realizados mostraram que o MIP sintetizado apresentou grande potencial para aplicacao em tecnica de SPE.